This invention relates to electrically powered fork lift trucks. More specifically, the present invention relates to alternating current inverters and motors for such trucks.
Industrial trucks such as forklift trucks are used for transporting heavy materials within warehouses, for stacking goods, and for other well known useful purposes. Such industrial trucks are often powered by a large lead acid battery. In such trucks electric motors are used to convert the battery's electrical power for propelling the machine, lifting the pay load, steering the machine, and for other useful purposes. Recent technology improvements in solid state power electronics have made the use of alternating current (AC) electrical motors a practicality through the advent of improved inverters. Battery powered inverters are an electronic device that convert the battery's direct current energy into three phase alternating current energy of an adjustable frequency and adjustable voltage level to create the desired performance of an electrical motor. The same functions are sometimes accomplished through the use of fuel cell power sources, hybrid, and other electrical power sources. The present invention applies to all electrically powered industrial trucks regardless of chemistry of a storage battery that is used with any other source of the electrical power.
In current forklift trucks, multiple electric motors that use multiple AC inverters are used. The system cost of using one inverter for each motor can be excessive. In many cases, the inverter cost is a serious drawback for OEMs (original equipment manufacturers) that want to go to maintenance free AC solutions. Consequently, problems remain in the art regarding the cost of using a plurality of motors, and regarding the amount of space the extra inverters take up in order to supply power to extra motors.
Therefore, there is a need in the art for an inverter that will be battery powered from a truck's lead acid battery that will have a power module that is able to power a plurality of motors. Additionally, there is a need in the art to provide for such a power module that will allow an inverter to be housed within the motor. Also, there is a need for a system that will properly cool this power module to ensure proper functioning.
Additionally, there is a need in the art for a means of configuring a single power module to independently control two electric motors. Due to the high cost of tooling that would be required to produce a completely new power module design, it is important to provide means of producing a tandem power module which uses existing power module packaging designs. To further reduce the cost of providing multiple models of inverters with a minimum number of different power modules, there is also a need in the art to optionally use a single power module design to either power a single electric motor of a higher current draw rating. In this manner the present invention teaches a means of producing a single power module that may be used in either a tandem inverter of moderate rating or in a single inverter of higher rating.
Therefore, it is a principal object of the present invention to provide an improved inverter that allows the inverter to power a plurality of motors.
Yet another object of the present invention is to provide for a cooling system that uses hydraulic fluid in order to cool the inverter.
Yet another object of the present invention is to provide for a cooling system that uses hydraulic fluid in order to cool the inverter.
Still another object of the present invention is to provide a single power module that may optionally be connected to supply a single electric motor of high current draw.
Yet another object of the present invention is to provide a single power module that may optionally be connected to control more than one electric motor of moderate to current draw.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claims.